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Facade retrofit

Our interesting case study of an innovative cheap non-intrusive facade retrofit of a 10-year old office building that significantly improved energy efficiency, thermal comfort, daylight, views out as well as reducing traffic noise from outside.

This office building had an ordinary facade design consisting of a 1 meter high parapet wall, a 1.7 meter tall window, and a suspended ceiling space. The standard aluminium window frames were leaky, as evident from the significant traffic noise entering through the closed single pane windows for this office located along a busy road in central Jakarta. When opening the windows, the window gasket had hardened over time and was also partially missing making it impossible for the windows to close tight. Moreover, as is often the case for cheap windows, the frame of some of the openable windows had slightly warped, making it impossible to fully close them tightly.

Another source of unexpected air-leakage occurred out of sight, namely in the suspended ceiling space. It turned out that above the facade window there was no solid board connecting to the concrete soffit above. In other words, the suspended ceiling space of the office was only separated from the outside by the leaky facade panels. What made matters worse was the fact that this air-conditioning system was designed for open return above the suspended ceiling. Hence, the return air going back to the AHU, would not only draw air from the offices, but also air from outside.

For the retrofit of the facade, we decided to go with the cheaper, faster and less intrusive option of leaving the existing windows in place. Instead, we had custom-made thin clear-glass aluminium windows mounted from the inside onto the existing window frames. As such, the office was upgraded to have double-glazed windows (DGU), albeit not with the benefits of spectrally selective window coatings. Nevertheless, this retrofit slashed the thermal transmittance of the windows to half. More importantly, the extra window layer ensured an air-tight facade, which both would reduce the energy consumption for cooling and dehumidification, but also audibly reduced the traffic noise level in the office.

For easy maintenance, the added clear glass window frames were mounted with screws, so they could easily be removed for window polishing. Moreover, the new window panes placed in front of the openable windows were fitted with fixed handles for easy removal, in case the occupants wish to open the window; albeit rarely the case for air-conditioned office environments.

An air-tight and acoustic insulating board was installed in the suspended ceiling space above the facade windows to ensure that the entire facade was fully sealed from the outside.

The daylight autonomy of the office was also greatly improved by undertaking following facade retrofits. Firstly, a lightshelf was place on the outside window sill. The 600 mm deep mirror reflective lightshelf was tilted slightly outwards, so it would not cause glare to occupants while working at their desks. For glare control, the existing office had manually adjustable vertical blinds curtain installed, which were almost always engaged, hence, cutting most of the daylight and views out. For the retrofit, the existing shading system was replaced with adjustable horizontal perforated venetian blinds that worked hand-in-hand with the lightshelf, as light reflected off the lightshelf would travel more or less unobstructed in through blinds, as the direction of the reflected light would be parallel to the blind position. The perforation of the venetian blinds would ensure that the view out would be retained, even if the blinds were closed completely.

The above photo clearly shows how the daylight reflected from the lightshelf spills onto the ceiling. The improved and glare-free daylight design meant that the electric lights hardly ever were turned on after the retrofit.


Further information about our office retrofit, which achieved 53% measured energy savings, can be found here:

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